Automatic tool exchanger

Abstract: A simple and efficient tool exchanger device is presented. The device has a pair of swing arms (8, 9), and each swing arm is provided with a set of grippers (11, 12) for holding a tool bit. The positions of the swing arms (8, 9) are separated by 90 degree so that they will not interfere with each other during the swinging motion. One driving device (2) is provided to operate both swing arms (8, 9) and operate the gripper devices (11, 12). The swing arm (8) rotates upwards to remove a used tool bit (10) from the machining shaft (21) of a machining center and the other swing arm (9) is rotated downwards to install a new tool bit (10') in the vacated machining shaft in a single simultaneous step.

Description: The present invention relates to a device for automatically exchanging tools between a main machining axis and a tool magazine. Productivity improvement is one of the basic requirements of a machining centre. With an improvement in cutting efficiency being achieved in modern machining centres, there is a strong need for shortening the non-cutting time particularly for light alloy fabrication operations which generally require short cutting time. There is thus an important need for shortening the time required for exchanging the tools between machining steps, because such steps occupy almost 20 percent of the total machining cycle time. To date, various tool exchanger devices have been disclosed, for example, in JP-A-5016047, JP-B-61053182 and JP-U-61042755. Such a device typically performs the following steps: gripping a tool, a used tool which has completed its job, disposed in the spindle of the machine centre, removing the used tool from the tapered hole of the spindle exchanging the position of the used tool disposed on a line of the extension of the spindle with another tool to be used in the same position, inserting this tool in the tapered hole of the spindle and releasing the hold on the spindle so that it can rotate and move into an operating position. However, such a device tries to improve the machining efficiency by speeding up the steps by using hydraulic or mechanical transmission systems. The conventional device of this type suffered from the following problems. a) There is a large motion range (the path of travel made by the tools to be exchanged), and the improvement is limited basically by the acceleration achievable within the speed attained by the tool. b) For each motion of the steps, acceleration and deceleration periods are required, and a time lag is generated. c) Various mechanisms are required for performing the various steps, and the device becomes complex to make, thus increasing the chances of device breakdowns. It is known from US-A-4575918 to provide an automatic tool exchanger comprising a support frame, a driving bevel gear, freely rotatably supported on said support frame, a driving means having an output shaft engaged to said driving bevel gear for rotating said driving bevel gear, a pair of follower bevel gears disposed on both sides of said driving bevel gear and engaged therewith, a pair of rotating shafts freely rotatably disposed on said support frame on both sides of said output shaft, a pair of swing arms each having a gripper device disposed on one end thereof, the opposite end of each swing arm being fixed to the outer end of each of said rotating shafts wherein said driving means drives each rotating shaft to swing said pair of swing arms simultaneously in one common direction thereby causing the gripper device of one swing arm to remove a used tool from a spindle of a machine while simultaneously enabling the gripper device of the other swing arm to insert a new tool in said spindle vacated by said used tool. The tool exchanger device of the present invention was made to resolve the problems outlined above, and the purpose is to present a device which can be manufactured easily and able to perform the exchange of tools automatically and reliably. According to an aspect of the invention there is provided an automatic tool exchanger in which the central axis of each of said pair of rotating shafts crosses on a point lying on the central axis of said output shaft, each of said rotating shafts being fixed to each follower bevel gear for rotation therewith. A feature of the device is that an output shaft of the driving device has a bevel gear to engage with a follower bevel gear disposed on the rotating shaft and another follower gear disposed on the other rotating shaft. A feature of the device is that the rotating shafts are separated by a 90 degree separation angle. The device presented above has a pair of rotation shafts each of which is provided with a swing arm having a set of gripper devices. The swing arms can be rotated freely without interfering with each other so that the tool used for machining disposed on the spindle of the machine centre is removed by one set of grippers disposed on one swing arm and a new tool installed on the spindle of the machining centre simultaneously by the set of grippers disposed on the other swing arm. The action of the device described above is made possible by disposing a bevel gear on the output shaft of the driving device so as to drive the two rotation shafts by means of a follower bevel gear disposed on each of the rotation shafts. Such an arrangement of the driving mechanism produces a simple and durable device which does not generate errors and breakdowns thus providing reliable machining operations. The device of such a construction is advantageous compared with the conventional devices for automatic changing of tools because the steps required in the conventional devices such as removing the tool from the spindle of the machine centre; switching the used tool with a new tool; installing the new tool in the spindle of the machining centre; are eliminated and replaced with one step of simultaneously removing the used tool from the spindle and installing the new tool in the spindle of the machining centre. Therefore, the entire operation of exchanging the tools is carried out efficiently to improve the machining operation of the machining centre. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a fragmented front view of the main parts of an embodiment of the device of the present invention for automatically exchanging tools; Figure 2 is a perspective view of the embodiment seen from the left towards the right in Figure 1; Figure 3 is a perspective view of the embodiment seen from the right towards the left in Figure 1; FIGURE 4 is a side view showing the positional relationship between the spindle of a machining centre and a pair of rotating arms; FIGURE 5 is a schematic illustration of the device of the present invention installed on a machining centre; FIGURE 6 is a side view of the machining centre shown in Figure 5. An embodiment of the present invention will be explained with reference to Figures 1 to 4. A tool exchanger device A in Figure 1 is a device for automatically exchanging tools and comprises a support frame 1 and a driving mechanism 2 firmly fixed on the support frame 1 as well as the rotating shafts 3,4 supported by the bearings 1a,1b. The driving mechanism 2 comprises electric and hydraulic motors, and associated actuators. A bevel gear 5 having a bearing 1c is attached to the bottom end of an output shaft 2a by a fixing device 2b. The pair of rotating shafts 3,4 are disposed symmetrically on the left and right sides of the output shaft 2a, and the extension lines from the centres of the rotating shafts 3,4 cross each other at the extension line of the centre line of the output shaft 2a at the base of the output shaft 2a of the bevel gear 5. Above the upper end of the rotating shafts 3,4 there are follower bevel gears 6,7 which are supported by the fixing devices 3a,4a and engaged with the bevel gear 5. Swing arms 8,9 having a 90 degree separation angle are fixed to the rotating shaft 3,4 respectively by fixing devices 3b,4b (4b is not shown). Each swing arm 8,9 is respectively provided with a set of gripper devices 11,12 at their free ends for grasping a tool 10,10'. The swing arms 8,9 with the gripper devices 11,12 are disposed symmetrically, and are driven by the driving device 2. The motions of the swing arms 8,9 are as follows: they rotate 90 degrees simultaneously within a plane about the spindle 21 of a machining centre B; resulting in that the swing arm 8 removes the gripper device 11 from the operating position (the position of the swing arm 8 in Figure 1) to a ready position (the position of the swing arm 9 in Figure 1) at the same time as the swing arm 9 moves the gripper device 12 from the stand-by position to the operating position. The designs of the gripper devices 11,12 are known, as are the hooks 11a,12a which elastically hold the tool 10,10'. The tool exchanger device A of the above configuration is disposed between a spindle 21 of a machining centre B and a tool magazine 22 as shown in Figures 5 and 6. The support frame 1 is attached to a guide rod 23, as shown in Figure 6, and is freely movable in the directions of X- and Y-axis. The spindle 21 is freely movable in the directions of X-, Y- and Z-axis. The X-axis direction is left/right, the Y-axis direction is up/down and the Z-axis direction is at right angles to the plane of the paper in Figure 5. The tool magazine 22 shown in Figure 6 comprises an endless chain 24 having a plurality of links provided with tool holder (not shown), driven by pulleys 25,26 and 27. Each of the tool holders in the tool magazine 22 holds the new tool 10' in the X-axis direction. The tool magazine 22 also rotates the tool pots, which serve as the shell for the shank part of tool 10', 90 degrees in the horizontal direction so as to orient the tool axis in the Z-axis direction at the pulley 25. This is shown a D in Figure 5. The machining centre B is a known conventional type. The operation of the tool exchanger device A of the present invention is explained as follows. A tool 10,10' (new or used) is installed on the gripper device 11 of the swing arm 8 or the gripper device 12 of the swing arm 9 by the following steps. Referring to Figure 5, the device A is moved in the X-axis direction from the stand-by position relative to the spindle 21 or the tool magazine 22. Either the gripper device 11 of the swing arm 8 or the gripper device 12 of the swing arm 9 is disposed directly above the spindle 21 of the machining centre which has been moved to the first exchange position C, or directly above the second exchange position D of the tool 10,10' taken out of the tool magazine 22 and disposed so that its shaft lies parallel to the spindle 21. The device A is then lowered relative to the spindle 21 or to the tool 10,10' of the tool magazine 22. The tool 10,10' of the tool magazine 22 to be held in the gripper devices 11,12 has been oriented in the Z-axis direction by the rotation of the holding device of the endless chain 24. When the tool 10,10' (new or used) is to be removed from the gripper devices 11,12, the device A is raised vertically relative to the spindle 21 of the machining centre when the tools 10,10' held in the gripper devices 11,12 are attached to the spindle 21 or to the tool magazine 22. When the tool 10,10' (new or used) is to be exchanged between the spindle 21 and the tool magazine 22, a used tool 10 is first held in one of the gripper devices 12, for example, of the swing arm 9 folded to the bottom side, and then the driving device 2 is operated. The operation of the driving device 2 makes the swing arm 9, having the used tool 10 in its gripper device 12, swing upwards, thereby removing the used tool 10 from the tool magazine 22 and assume a horizontal position. The swing arm 8, having an empty gripper device 11, rotates downward at the same time as the swing arm 9 rotates upwards. Next, the tool exchanger device is raised upwards, and is then moved in the X-axis direction to dispose the empty gripper device 11 of the swing arm 8 to a location above the spindle 21 of the machining centre. The device A is then lowered so that the gripper device 11 can grip the used tool 10 disposed in the spindle 21 of the machining centre. This condition is illustrated in Figure 1. The driving device 2 is now driven in the reverse direction to the above preparatory step. By this action, the swing arm 8 is rotated upwards, thereby removing the used tool 10 from the spindle 21 and assumes a horizontal position. At the same time the other swing arm 9 rotates downward as the swing arm 8 is moving upwards, and installs a new tool 10' in the now vacated spindle 21. After this step, the device A is raised upwards away from the spindle 21 to remove the gripper device 11 from the new tool 10'. The machining centre B is now ready to perform a machining operation using the new tool 10'. By following the similar steps, the used tool 10 disposed on the swing arm 8 is returned to the tool magazine 22, thereby completing the exchange operation. In the above descriptions, it is understood that the sequence of operations taken by the spindle 21 and the tool magazine 22 are general in nature, and other sequences are possible depending on the type of tool magazine and other details of the equipment. In the embodiment illustrated, each tool is identified by the chain numbers of the tool magazine, and tool management is facilitated. The tool pots are random with respect to the tools and the chain, and this arrangement is useful in shortening the preparation time for readying the next tool. The above embodiment is a case of driving two swing arms 8,9 at the same speed with one driving device 2, and mechanical interference between the two swing arms 8,9 is avoided by positioning them suitably. It is also possible to avoid interferences by delaying the starting times for one swing arm relative to the other swing arm, by altering the speeds of the swing arms. Therefore, it is possible to avoid mechanical interferences by using the positional elements as well as chronological elements. However, as long as even a part of the operation of the swing arms 8,9 is duplicated, such duplication times can be shortened, therefore, the meaning of simultaneous rotation, or rotating at the same time, includes the cases in which the rotations of the swing arms 8,9 partly overlap each other.

Claims: An automatic tool exchanger comprising a support frame (1), a driving bevel gear (5), freely rotatably supported on said support frame (1), a driving means (2) having an output shaft (2a) engaged to said driving bevel gear (5) for rotating said driving bevel gear (5), a pair of follower bevel gears (6,7) disposed on both sides of said driving bevel gear (5) and engaged therewith, a pair of rotating shafts (3,4) freely rotatably disposed on said support frame (1) on both sides of said output shaft (2a), a pair of swing arms (8,9) each having a gripper device (11,12) disposed on one end thereof, the opposite end of each swing arm (8,9) being fixed to the outer end of each of said rotating shafts (3,4) wherein said driving means (2) drives each rotating shaft (3,4) to swing said pair of swing arms (8,9) simultaneously in one common direction thereby causing the gripper device (11,12) of one swing arm (8,9) to remove a used tool (10) from a spindle (21) of a machine while simultaneously enabling the gripper device (11,12) of the other swing arm (8,9) to insert a new tool (10') in said spindle (21) vacated by said used tool (10) characterised in that the central axis of each of said pair of rotating shafts (3,4) crosses on a point lying on the central axis of said output shaft (2a), each of said rotating shafts (3,4) being fixed to each follower An automatic tool exchanger as claimed in claim 1 characterised in that said driving means (2) comprise rotational means including an electric motor and/or hydraulic motor, and an output shaft (2a) of said driving means (2) is operatively attached to said driving bevel gear (5). An automatic tool exchanger as claimed in claim 1 or claim 2 characterised in that said pair of rotating shafts (3,4) are disposed symmetrically on both sides of said output shaft (2a), said pair of follower bevel gears (6,7) are provided with the same number of teeth, and said pair of swing arms (8,9) rotate at the same rotational speed. An automatic tool exchanger as claimed in any preceding claim characterised in that the swing arms (8,9) are each fixed on the outer ends of the rotating shafts (3,4) with a 90 degrees phase separation angle. An automatic tool exchanger as claimed in any preceding claim characterised in that said support frame (1) has a box shaped portion, within which are housed said driving bevel gears (5) and said pair of follower bevel gears (6,7), wherein said outer part of said rotating shafts (3,4) are protruding out of said box shaped portion of said support frame (1). An automatic tool exchanger as claimed in claim 5 characterised in that said driving bevel gear (5) is freely rotatably supported on a central bottom part of said boxed shaped portion, a driving source for said driving means (2) is disposed on a top part of said box shaped portion, said pair of rotating shafts (3,4) whose centre lines cross at a location above said driving bevel gear (5) are freely rotatably supported on said bottom part of said box shaped portion, said pair of follower bevel gears (6,7) engaged on both sides of said driving bevel gear (5) are fixed to an interior part invading into said box shaped portion, and said swing arms (8,9) are fixed to an outer part of each of said rotating shafts (3,4) which are protruding out of the bottom part of said box shaped portion in an outer direction. An automatic tool exchanger as claimed in any preceding claim characterised in that said support frame (1) is provided with a pair of support arms which freely rotatably support an outer terminal end of each of said rotating shafts (3,4). An automatic tool exchanger as claimed in any preceding claim characterised in that said pair of swing arms (8,9) are fixed respectively to said rotating shafts (3,4) at a 90 degree phase separation angle so that when said one swing arm (8,9) is positioned vertically down with respect to said support frame (1), said other swing arm (8,9) is positioned horizontally up in front of said support frame (1).

Inventors: SATO KYUICHI, TAMURA YUKIO, SATO, KYUICHI, TAMURA, YUKIO
Applicants: NIIGATA ENGINEERING CO LTD, NIIGATA ENGINEERING CO., LTD.
Application year: 1994
Main classification: B23Q3
IPC codes: B23Q3